Officials said after the 23-year-old’s arrest by the FBI on Wednesday that he was indicted by a grand jury in the Eastern District of Wisconsin in relation to charges in the year leading up to July 2015.

Hutchins, also known as MalwareTech, was hailed a hero in May this year when he found a “kill-switch” that slowed the effects of the WannaCry “ransomware” virus that hit more than 300,000 computers in 150 countries.

The investigation predates that attack and is completely unrelated, officials said.

The indictment says Hutchins created the Kronos malware before conspiring with another defendant, whose name has been redacted, to advertise and sell it on internet forums.

In August 2014 the unnamed defendant sold the software for 2,000 dollars (£1,522) in a digital currency in June 2015, the legal document adds.

Hutchins’ mother, Janet Hutchins, said it was “hugely unlikely” that her son was involved because he has spent “enormous amounts of time and even his free time” combating such attacks.

She said she is “outraged” by the charges and has been “frantically calling America” trying to contact her son.

A friend from the IT security industry, who spoke on the condition of anonymity, said Hutchins was arrested in McCarran International Airport after he tried to fly back from the Def Con hacking conference.

The Electronic Frontier Foundation, a San Francisco-based digital rights group, said it is “deeply concerned” and has reached out to Hutchins.